Path: utzoo!utgpu!news-server.csri.toronto.edu!me!zougas
Newsgroups: comp.object
From: zougas@me.utoronto.ca ("Athanasios(Tom) Zougas")
Subject: Re: How would you model this situation?
Message-ID: <90Oct17.222508edt.20472@me.utoronto.ca>
Organisation: U of Toronto, Dept. of Mechanical Engineering
Organization: Mechanical Engineering, U of Toronto
References: <16734@rouge.usl.edu>
Date: 18 Oct 90 02:25:25 GMT

pcb@cacs.usl.edu (Peter C. Bahrs) writes:

>The Domain: Object-oriented with concurrency if needed, objects have
>     local state, behaviors

>The Problem:
>  Model an application where two things(people) ara each applying a 
>force(pulling) on another thing (ends of a rope).  The acted upon
>thing (the rope) breaks.

>So suppose I tell person1 to pull X amount.  Should I model all of
>the interactions at an application level and then send the rope and 
>person2 reactionary messages.  Or should person1, who knows about a
>rope (globally) tell the rope to adjust it self, which in turn must
>tell person2 to adjust hisself.  So if the rope breaks, how are the
>references in person1 and person2 updated?  Does the existing rope
>references become forwarders to new part-rope objects?  In summary,
>are interactions managed external to objects or should this be
>migrated inside the objects.

If we were to take the approach that we want to simulate what happens
in reality, we may get the following:
	o person1 is told to pull by X
	o person1 transmits the message to the rope, another 'object',
		that it is pulling by X
	o the rope responds according to its physics, tell person2 that
		it is pulling him be X amount
	o person2 has to have some type of boundary condition to be
		able to react to the rope's message (pull back to
		remain motionless, fall down, etc.)
	o if the rope breaks it tells person1 and person2 that it no
		longer will support their forces, and they responc accordingly
This situation is essentially a set of simultaneous equations that need to
be solved. The steps described above are simply the steps in solving the
equations. An analog I see to the above is the field of finite elements
were the people are the boundary conditions, the rope the element, and
the ends of the rope, the nodes.

Just some thoughts from...
Tom.
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